Electrically controlled audible devices are so ubiquitous that the casual hearer seldom considers the wide range and quality of sounds that are produced by the various devices. Audible devices may include common doorbells, chimes, fire alarms, police or fire sirens, and many other varieties which will occur to one who listens with discrimination. In order to be able to describe the various types of sounds that are produced, an attempt has been made, within the industry, to assign names to the various sounds. These names have included: fast whoop; slow whoop; wail; horn; hi-lo; chimes; yeow; ding-dong; bell; warble; yelp; beep; and stutter. Other and/or alternate names have also been employed. At least on a local basis, certain types of audible sounds have become associated with certain emergency conditions or activities. For example, although there may not be an entirely universal sound for police sirens, it is conventional for all police vehicles, in any given locality, to employ an identical sound. By convention, anyone else needing an alarm sound would employ a different tone. Thus, the fire fighting vehicles, ambulances, and air raid warning signals would all have a different characteristic making it easy for the hearer to identify the meaning of the sound. Within large buildings such as offices, factories, department stores, hospitals, schools, etc., it is often desirable to be able to produce different tones indicative of selected conditions. For example, it might be desirable to use audible devices to indicate such conditions as: start time; end time; change time; lunch time; stand by for voice message; evacuate the building; fire alarm; dangerous condition; or any number of other conditions which it may be desirable to signal by audio device according to the needs and operation of the facility.
In those situations wherein it is desirable to be able to selectively produce one of a plurality of different audio signals, it is convenient and economical to be able to produce the full range of audio signals with a single device thereby eliminating the need for multiple devices and control systems. Systems with these features and characteristics are not broadly new and are believed to be too familiar to require further elaboration.
The present invention relates to a convenient, compact, and economical device which is capable of selectively producing any one of a plurality of distinguishable, audible signals. U.S. Pat. No. 4,065,767 issued Dec. 27, 1977 to Jacob Neuhof et al. and assigned to the same assignee as the present invention discloses a programmable electronic siren and the means for controlling it. While the present invention may have some features and characteristics in common with the cited patent, it will be shown that the structure of the present invention includes numerous features and characteristics combined with convenience and economy which are not available in the prior art. Other devices having some features or characteristics in common with the present invention are disclosed in the following patents:
U.S. Pat. No. 3,137,846 issued June 16, 1964 to H. G. Keeling and entitled Electronic Siren; PA1 U.S. Pat. No. 3,882,275 issued May 6, 1975 to G. S. Carroll and entitled Sound Communication System; PA1 U.S. Pat. No. 3,889,256 issued June 10, 1975 to R. F. Sieslak et al and entitled Automatic Control for Audible Electronic Warning System; PA1 U.S. Pat. No. 3,905,016 issued Sept. 9, 1975 to C. J. Peterson and entitled Reverse Signal Alarm System; PA1 U.S. Pat. No. 3,981,007 issued Sept. 14, 1976 to R. F. Sieslak et al and entitled Industrial Control for Audible Electronic Warning System; and PA1 U.S. Pat. No. 4,016,496 issued Apr. 5, 1977 to P. Eastcott and entitled Method and Apparatus for Producing Ramp Signals with Rounded Inflection Points.